This invention relates to an improved burner for use in a liquid candle and in particular for use in either a disposable or a refillable liquid candle.
The term liquid candle as herein used refers to a heating or lighting device wherein liquid fuel is wicked from a fuel reservoir into a burning region via capillary action where the fuel is vaporized and then ignited to produce a flame about the exposed tip of a wick. The amount of heat or illumination produced by the candle is a function of the wick length that is exposed to atmosphere within the burning region. In many lighting applications, the length of the wick is fixed in the factory to provide a relatively low flame of the type normally associated with a more conventional solid wax candle. A wide variety of liquid fuels can be burned in a liquid candle, however, liquid paraffin is preferred because of its clean burning characteristics. Even when burning a high grade fuel, a liquid candle can produce some out gassing of the fuel vapors. The escape of these vapors to the surrounding atmosphere is objectionable for two reasons. First, many liquid fuel vapors have a clearly discernable, and sometimes unpleasant, odor that may remain in the surrounding atmosphere for long periods of time. Secondly, the escaped vapors can condense on surrounding surfaces thereby "wetting" the host object with an undesirable film. The escape of vapors from the fuel reservoir usually takes place through a vapor vent formed in an otherwise sealed fuel container. The vent is needed to equalize the internal pressure of the container with surrounding atmospheric pressure so that the wicking action can be sustained. Liquid candles utilizing this type of venting arrangement are disclosed in U.S. Pat. Nos. 4,261,695 and 3,799,731.
An early U.S. Pat. No. 545,313 describes a liquid candle that is designed to sustain a low level of illumination over a relatively long period of time. As noted in this patent, low illumination settings as typically used in lamp for providing intimate table lighting, sometimes do not allow for the complete vaporization of the fuel resulting in a wet wick. The unburned fluid brought to the burning zone can cause problems if not efficiently removed from the burning area. A bulb-like chamber is provided in the disclosed burner through which a base wick is passed just prior to its entering the burning zone. The chamber acts as a preheater to promote vaporization of the wicked fuel and also serves to collect any excess fuel brought into the burning zone. A similar type burner for preventing the accumulation of excessive fuel about the exposed tip of the wick is disclosed in U.S. Pat. No. 3,321,938 wherein the fuel is collected in a closed conduit which carries the fuel back to the fuel reservoir. In order for the excess fuel to flow under the influence of gravity back into the fuel reservoir, the conduit opening must be large enough to permit the collected fuel to overcome both the normal surface tension associated with a small vent and the internal pressure found in the reservoir. When the vent is made large enough to permit efficient drainage, it also provides a means through which the fuel can easily escape from the reservoir in the event the unit is tipped either during shipping or normal usage. Large quantities of fuel can thus be lost from the container to the surrounding area where it can cause unwanted damage.
In a U.S. Pat. No. 4,126,408 which issued to Cox, a disposable liquid candle is sealed within a closed fuel container. The burner is a simple metal tube that passes downwardly through the tip of the container into the fuel reservoir. The top of the burner tube is contained within a cylindrical trap that also serves as the male connector for a screw on cap. The burner tube is packed with asbestos at the upper end thereof and a wicking material throughout the lower section. A small position of the wick is exposed below the top of the trap and provides a burning site for a low flame. Any excessive fuel brought to the exposed end of the burner is collected in the trap and returned to the reservoir by means of a drain. The wick is fully enclosed within the trap to enable the cap to be screwed thereon when it is desirous to close and seal the unit.
The use of disposable liquid candles, such as that described by Cox, is highly desirous in restaurants, clubs and other public gathering places because they eliminate many of the problems associated with filling, cleaning and otherwise maintaining a reusable unit. In these disposable units, the wick is generally preset in the factory to provide optimum aesthetic balancing of the flame while still providing for economy of operation. It is also desirous to lock the wick in a preset condition so that it can not be tampered with by patrons or workers. Providing the disposable units with an acceptable shelf life without loss of fuel while at the same time protecting the wick from damage has long been a problem of the art.